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Message-Id: <20210802180903.159381-1-mizhang@google.com>
Date: Mon, 2 Aug 2021 11:09:03 -0700
From: Mingwei Zhang <mizhang@...gle.com>
To: Paolo Bonzini <pbonzini@...hat.com>
Cc: Sean Christopherson <seanjc@...gle.com>,
Vitaly Kuznetsov <vkuznets@...hat.com>,
Wanpeng Li <wanpengli@...cent.com>,
Jim Mattson <jmattson@...gle.com>,
Joerg Roedel <joro@...tes.org>, kvm@...r.kernel.org,
linux-kernel@...r.kernel.org, Mingwei Zhang <mizhang@...gle.com>,
Tom Lendacky <thomas.lendacky@....com>,
Marc Orr <marcorr@...gle.com>,
David Rientjes <rientjes@...gle.com>,
Alper Gun <alpergun@...gle.com>,
Dionna Glaze <dionnaglaze@...gle.com>,
Vipin Sharma <vipinsh@...gle.com>,
Peter Gonda <pgonda@...gle.com>
Subject: [PATCH v2] KVM: SVM: improve the code readability for ASID management
KVM SEV code uses bitmaps to manage ASID states. ASID 0 was always skipped
because it is never used by VM. Thus, in existing code, ASID value and its
bitmap postion always has an 'offset-by-1' relationship.
Both SEV and SEV-ES shares the ASID space, thus KVM uses a dynamic range
[min_asid, max_asid] to handle SEV and SEV-ES ASIDs separately.
Existing code mixes the usage of ASID value and its bitmap position by
using the same variable called 'min_asid'.
Fix the min_asid usage: ensure that its usage is consistent with its name;
allocate extra size for ASID 0 to ensure that each ASID has the same value
with its bitmap position. Add comments on ASID bitmap allocation to clarify
the size change.
v1 -> v2:
- change ASID bitmap size to incorporate ASID 0 [sean]
- remove the 'fixes' line in commit message. [sean/joerg]
Signed-off-by: Mingwei Zhang <mizhang@...gle.com>
Cc: Tom Lendacky <thomas.lendacky@....com>
Cc: Marc Orr <marcorr@...gle.com>
Cc: David Rientjes <rientjes@...gle.com>
Cc: Alper Gun <alpergun@...gle.com>
Cc: Dionna Glaze <dionnaglaze@...gle.com>
Cc: Sean Christopherson <seanjc@...gle.com>
Cc: Vipin Sharma <vipinsh@...gle.com>
Cc: Peter Gonda <pgonda@...gle.com>
Cc: Joerg Roedel <joro@...tes.org>
---
arch/x86/kvm/svm/sev.c | 36 +++++++++++++++++++++---------------
1 file changed, 21 insertions(+), 15 deletions(-)
diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
index 8d36f0c73071..42d46c30f313 100644
--- a/arch/x86/kvm/svm/sev.c
+++ b/arch/x86/kvm/svm/sev.c
@@ -63,6 +63,7 @@ static DEFINE_MUTEX(sev_bitmap_lock);
unsigned int max_sev_asid;
static unsigned int min_sev_asid;
static unsigned long sev_me_mask;
+static unsigned int nr_asids;
static unsigned long *sev_asid_bitmap;
static unsigned long *sev_reclaim_asid_bitmap;
@@ -77,11 +78,11 @@ struct enc_region {
/* Called with the sev_bitmap_lock held, or on shutdown */
static int sev_flush_asids(int min_asid, int max_asid)
{
- int ret, pos, error = 0;
+ int ret, asid, error = 0;
/* Check if there are any ASIDs to reclaim before performing a flush */
- pos = find_next_bit(sev_reclaim_asid_bitmap, max_asid, min_asid);
- if (pos >= max_asid)
+ asid = find_next_bit(sev_reclaim_asid_bitmap, nr_asids, min_asid);
+ if (asid > max_asid)
return -EBUSY;
/*
@@ -114,15 +115,15 @@ static bool __sev_recycle_asids(int min_asid, int max_asid)
/* The flush process will flush all reclaimable SEV and SEV-ES ASIDs */
bitmap_xor(sev_asid_bitmap, sev_asid_bitmap, sev_reclaim_asid_bitmap,
- max_sev_asid);
- bitmap_zero(sev_reclaim_asid_bitmap, max_sev_asid);
+ nr_asids);
+ bitmap_zero(sev_reclaim_asid_bitmap, nr_asids);
return true;
}
static int sev_asid_new(struct kvm_sev_info *sev)
{
- int pos, min_asid, max_asid, ret;
+ int asid, min_asid, max_asid, ret;
bool retry = true;
enum misc_res_type type;
@@ -142,11 +143,11 @@ static int sev_asid_new(struct kvm_sev_info *sev)
* SEV-enabled guests must use asid from min_sev_asid to max_sev_asid.
* SEV-ES-enabled guest can use from 1 to min_sev_asid - 1.
*/
- min_asid = sev->es_active ? 0 : min_sev_asid - 1;
+ min_asid = sev->es_active ? 1 : min_sev_asid;
max_asid = sev->es_active ? min_sev_asid - 1 : max_sev_asid;
again:
- pos = find_next_zero_bit(sev_asid_bitmap, max_sev_asid, min_asid);
- if (pos >= max_asid) {
+ asid = find_next_zero_bit(sev_asid_bitmap, max_sev_asid, min_asid);
+ if (asid > max_asid) {
if (retry && __sev_recycle_asids(min_asid, max_asid)) {
retry = false;
goto again;
@@ -156,11 +157,11 @@ static int sev_asid_new(struct kvm_sev_info *sev)
goto e_uncharge;
}
- __set_bit(pos, sev_asid_bitmap);
+ __set_bit(asid, sev_asid_bitmap);
mutex_unlock(&sev_bitmap_lock);
- return pos + 1;
+ return asid;
e_uncharge:
misc_cg_uncharge(type, sev->misc_cg, 1);
put_misc_cg(sev->misc_cg);
@@ -1854,12 +1855,17 @@ void __init sev_hardware_setup(void)
min_sev_asid = edx;
sev_me_mask = 1UL << (ebx & 0x3f);
- /* Initialize SEV ASID bitmaps */
- sev_asid_bitmap = bitmap_zalloc(max_sev_asid, GFP_KERNEL);
+ /*
+ * Initialize SEV ASID bitmaps. Allocate space for ASID 0 in the bitmap,
+ * even though it's never used, so that the bitmap is indexed by the
+ * actual ASID.
+ */
+ nr_asids = max_sev_asid + 1;
+ sev_asid_bitmap = bitmap_zalloc(nr_asids, GFP_KERNEL);
if (!sev_asid_bitmap)
goto out;
- sev_reclaim_asid_bitmap = bitmap_zalloc(max_sev_asid, GFP_KERNEL);
+ sev_reclaim_asid_bitmap = bitmap_zalloc(nr_asids, GFP_KERNEL);
if (!sev_reclaim_asid_bitmap) {
bitmap_free(sev_asid_bitmap);
sev_asid_bitmap = NULL;
@@ -1904,7 +1910,7 @@ void sev_hardware_teardown(void)
return;
/* No need to take sev_bitmap_lock, all VMs have been destroyed. */
- sev_flush_asids(0, max_sev_asid);
+ sev_flush_asids(1, max_sev_asid);
bitmap_free(sev_asid_bitmap);
bitmap_free(sev_reclaim_asid_bitmap);
--
2.32.0.554.ge1b32706d8-goog
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